The present invention relates to a negative film masking apparatus provided with a trimming negative film masking for use in a photographic printer.
Photographic negative films are classified into a number of sizes (including 135F, 6.times.4.5, 6.times.6, 6.times.7, and 6.times.9).
For trimming and printing a portion of the frame of such a negative film, a negative film masking having a masking window of the same size as of the film frame has to be used in the prior art. It is thus needed for an operator of the photographic printer to remember the window size of the negative film masking to be used and input its data to or select a corresponding channel of the printer. However, the negative film masking when having been installed to a masking base in the photographic printer can hardly be examined for its window size and may be mishandled as a different size producing a fault print.
Such a conventional negative film masking apparatus of the photographic printer has a magnet-equipped masking base on which a magnetic plate carrying the negative film masking is placed and secured by a magnetic force.
The positional adjustment of the negative film masking is however limited due to unfavorable dimensional relation between the magnet and the magnetic plate, thus restricting the trimming action.
The magnetic force of the magnet is small enough to allow the negative film masking to move for adjustment. Accordingly, the masking tends to slip out from the masking base which is commonly arranged tilting due to a structural orientation in the photographic printer.
It is an object of the present invention, in view of the foregoing aspects, to provide an improved negative film masking apparatus for a photographic printer where a detector switch is disposed to protrude from the base surface of a masking base so that the type of a negative film masking loaded on the base surface can be examined for matching the type of a negative film, but not to disturb the trimming action.
It is another object of the present invention to provide a negative film masking apparatus for a photographic printer capable of securing a negative film masking tightly to the masking base for prevention of slipping-off.